The Photoplay | Page 2

the "Philosophical Transactions" an interesting optical
illusion of movement, resulting, for instance, when a wheel is moving
along behind a fence of upright bars. The discussion was carried much
further when it was taken up a few years later by a master of the craft,
by Faraday. In the Journal of the Royal Institute of Great Britain he
writes in 1831 "on a peculiar class of optical deceptions." He describes
there a large number of subtle experiments in which cogwheels of
different forms and sizes were revolving with different degrees of
rapidity and in different directions. The eye saw the cogs of the moving
rear wheel through the passing cogs of the front wheel. The result is the
appearance of movement effects which do not correspond to an
objective motion. The impression of backward movement can arise
from forward motions, quick movement from slow, complete rest from
combinations of movements. For the first time the impression of
movement was synthetically produced from different elements. For
those who fancy that the "new psychology" with its experimental

analysis of psychological experiences began only in the second half of
the nineteenth century or perhaps even with the foundation of the
psychological laboratories, it might be enlightening to study those
discussions of the early thirties.
The next step leads us much further. In the fall of 1832 Stampfer in
Germany and Plateau in France, independent of each other, at the same
time designed a device by which pictures of objects in various phases
of movement give the impression of continued motion. Both secured
the effect by cutting fine slits in a black disk in the direction of the
radius. When the disk is revolved around its center, these slits pass the
eye of the observer. If he holds it before a mirror and on the rear side of
the disk pictures are drawn corresponding to the various slits, the eye
will see one picture after another in rapid succession at the same place.
If these little pictures give us the various stages of a movement, for
instance a wheel with its spokes in different positions, the whole series
of impressions will be combined into the perception of a revolving
wheel. Stampfer called them the stroboscopic disks, Plateau the
phenakistoscope. The smaller the slits, the sharper the pictures.
Uchatius in Vienna constructed an apparatus as early as 1853 to throw
these pictures of the stroboscopic disks on the wall. Horner followed
with the daedaleum, in which the disk was replaced by a hollow
cylinder which had the pictures on the inside and holes to watch them
from without while the cylinder was in rotation. From this was
developed the popular toy which as the zoötrope or bioscope became
familiar everywhere. It was a revolving black cylinder with vertical
slits, on the inside of which paper strips with pictures of moving
objects in successive phases were placed. The clowns sprang through
the hoop and repeated this whole movement with every new revolution
of the cylinder. In more complex instruments three sets of slits were
arranged above one another. One set corresponded exactly to the
distances of the pictures and the result was that the moving object
appeared to remain on the same spot. The second brought the slits
nearer together; then the pictures necessarily produced an effect as if
the man were really moving forward while he performed his tricks. In
the third set the slits were further distant from one another than the
pictures, and the result was that the picture moved backward.

The scientific principle which controls the moving picture world of
today was established with these early devices. Isolated pictures
presented to the eye in rapid succession but separated by interruptions
are perceived not as single impressions of different positions, but as a
continuous movement. But the pictures of movements used so far were
drawn by the pen of the artist. Life showed to him everywhere
continuous movements; his imagination had to resolve them into
various instantaneous positions. He drew the horse race for the
zoötrope, but while the horses moved forward, nobody was able to say
whether the various pictures of their legs really corresponded to the
stages of the actual movements. Thus a true development of the
stroboscopic effects appeared dependent upon the fixation of the
successive stages. This was secured in the early seventies, but to make
this progress possible the whole wonderful unfolding of the
photographer's art was needed, from the early daguerreotype, which
presupposed hours of exposure, to the instantaneous photograph which
fixes the picture of the outer world in a small fraction of a second. We
are not concerned here with this technical advance, with the perfection
of the sensitive surface of the photographic plate. In 1872 the
photographer's camera had reached a stage at which it was possible